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Sixteen engineering approaches to low cost standardized payloads in spacecraft are presented. Standard earth observatory satellite, standard U.S. domestic communication satellite, planetary spacecraft subsystems, standard spacecraft, and cluster spacecraft are reviewed.
Measurements with several operational atomic hydrogen maser standards have been made which illustrate the fundamental characteristics of the maser as well as the analysability of the corrections which are made to relate the oscillation frequency to the free, unperturbed, hydrogen standard transition frequency. Sources of the most important perturbations, and the magnitude of the associated errors, are discussed. A variable volume storage bulb hydrogen maser is also illustrated which can provide on the order of 2 parts in 10 to the 14th power or better accuracy in evaluating the wall shift. Since the other basic error sources combined contribute no more than approximately 1 part in 10 to the 14th power uncertainty, the variable volume storage bulb hydrogen maser will have net intrinsic accuracy capability of the order of 2 parts in 10 to the 14th power or better. This is an order of magnitude less error than anticipated with cesium standards and is comparable to the basic limit expected for a free atom hydrogen beam resonance standard.
The procedures available for photometric calibration at extreme ultraviolet (EUV) wavelengths are outlined and the requirements for a secondary standard EUV photomultiplier defined. The performance of a number of commercially available channel electron multipliers over the 304-1350-A wavelength range is described, and their suitability for use as secondary standards is discussed in detail. Although none of the multipliers evaluated fully met the requirements for a secondary standard, it proved possible to calibrate absolutely a Mullard cone channel over the required wavelength range to an accuracy of plus or minus 9% and to employ it as a secondary standard in the calibration of a series of sounding rocket spectrometers.
In the course of testing various rubidium and cesium frequency standards under operational conditions for use in NASA tracking stations, about 55 unit-years of relative frequency measurements for averaging times from 10 to 10 to the 7th power have been accumulated at Goddard Space Flight Center (GSFC). Statistics on the behavior of rubidium and cesium standards under controlled laboratory conditions have been published, but it was not known to what extent the lesser controlled environments of NASA tracking stations affected the performance of the standards. The purpose of this report is to present estimates of the frequency stability of rubidium and cesium frequency standards under operational conditions based on the data accumulated at GSFC.
A description is given of the boron/epoxy and graphite/epoxy nondestructive test standards which were fabricated, tested and delivered to the National Aeronautics and Space Administration. Detailed design drawings of the standards are included to show the general structures and the types and location of simulated defects built into the panels. The panels were laminates with plies laid up in the 0 deg, + or - 45 deg, and 90 deg orientations and containing either titanium substrates or interlayered titanium perforated shims. Panel thickness was incrementally stepped from 2.36 mm (0.093 in.) to 12.7 mm (0.500 in.) for the graphite/epoxy standards, and from 2.36 mm (0.093 in.) to 6.35 mm (0.25 in.) for the boron/epoxy standards except for the panels with interlayered shims which were 2.9 mm (0.113 in.) maximum thickness. The panel internal conditions included defect free regions, resin variations, density/porosity variations, cure variations, delaminations/disbonds at substrate bondlines and between layers, inclusions, and interlayered shims. Ultrasonic pulse echo C-scan and low-kilovoltage X-ray techniques were used to evaluate and verify the internal conditions of the panels.
Situation and command head-up displays were evaluated for both standard and two segment noise abatement night visual approaches in a fixed base simulation of a DC-8 transport aircraft. The situation display provided glide slope and pitch attitude information. The command display provided glide slope information and flight path commands to capture a 3 deg glide slope. Landing approaches were flown in both zero wind and wind shear conditions. For both standard and noise abatement approaches, the situation display provided greater glidepath accuracy in the initial phase of the landing approaches, whereas the command display was more effective in the final approach phase. Glidepath accuracy was greater for the standard approaches than for the noise abatement approaches in all phases of the landing approach. Most of the pilots preferred the command display and the standard approach. Substantial agreement was found between each pilot's judgment of his performance and his actual performance.
The U.S. Standard Atmosphere, 1975 (COESA, 1975) is an idealized, steady-state representation of the earth's atmosphere from the surface of the earth to 1000-km altitude, as it is assumed to exist in a period of moderate solar activity. From 0 to 86 km, the atmospheric model is specified in terms of the hydrostatic equilibrium of a perfect gas, with that portion of the model from 0 to 51 geopotential kilometers being identical with that of the U.S. Standard Atmosphere, 1962 (COESA, 1962). Between 51 and 86 km, the defining temperature-height profile has been modified from that of the 1962 Standard to lower temperatures between 51 and 69.33 km, and to greater values between 69.33 and 86 km. Above 86 km, the model is defined in terms of quasi-dynamic considerations involving the vertical component of the flux of molecules of individual gas species. These conditions lead to the generation of independent number-density distributions of the major species, N2, O2, O, Ar, Ne, and H, consistent with observations. The detailed definitions of the model are presented along with graphs and abbreviated tables of the atmospheric properties of the 1975 Standard.
The ability to configure data systems using modules provided by independent manufacturers is complicated by the wide range of electrical, mechanical, and functional characteristics exhibited within the equipment provided by different manufacturers of computers, peripherals, and terminal devices. A number of international organizations were and still are involved in the creation of standards that enable devices to be interconnected with minimal difficulty, usually involving only a cable or data bus connection that is defined by the standard. The elements covered by an interface standard are covered and the most prominent interface standards presently in use are identified and described.
A hybrid microcircuit standard was developed after a thorough review of applicable NASA, military, industry, and technical society specifications and standards and compilation of comments from technical reviewers throughout the hybrid industry. The draft of the standard submitted to the technical reviewers, the comments from the reviewers, and the completed standard are discussed.
The NASA standardization effort which has been in existence for four years is described. A significant number of equipments have been declared standard in order to achieve multimission utilization with the consequent avoidance of high nonrecurring development costs. The small numbers of equipments and significant gaps in time before the next user requires the item raise questions of the value of maintaining a standard, how to assure its producibility economically in the future, and how to prevent its technical obsolescence. Increasing pressures to broaden the participation of industry in the space program have also contributed to a reexamination of the philosophy of standardization.
Industry, government, and NASA standards, and the status of standardization activities of standards setting organizations applicable to the design, implementation and operation of a data base management system for space related applications are identified. The applicability of the standards to a general purpose, multimission data base management system is addressed.
Standards needed to interconnect applications data service pilots for data sharing were identified. Current pilot methodologies are assessed. Recommendations for future work are made. A preliminary set of requirements for guidelines and standards for catalogues, directories, and dictionaries was identified. The user was considered to be a scientist at a terminal. Existing and emerging national and international telecommunication standards were adopted where possible in view of new and unproven standards.
Atomic standards such as those based upon cesium and hydrogen rely upon magnetic state selection to obtain population inversion in the hyperfine transition levels. Use of new design approaches and improved magnetic materials has made it possible to fabricate improved state selectors of small size, and thus the efficiency of utilization of beam flux is greatly improved and the size and weight of the standard is reduced. The sensitivity to magnetic perturbations is also decreased, so that the accuracy and stability of the standard is improved. Several new state selector designs are illustrated and the application to standards utilizing different atomic species is analyzed.
An experiment is reported where silver iodide is used to determine the standard free energy of formation of iron iodide. By using silver iodide as a solid electrolyte, a galvanic cell, Ag/AgI/Fe-FeI2, is formulated. The standard free energy of formation of AgI is known, and hence it is possible to estimate the standard free energy of formation of FeI2 by measuring the open-circuit emf of the above cell as a function of temperature. The free standard energy of formation of FeI2 determined by this method is -38784 + 24.165T cal/mol. It is estimated that the maximum error associated with this method is plus or minus 2500 cal/mol.
The presently reported effort to provide a single set of standards for the design, analysis and testing of Space Transportation System (STS) payloads throughout the NASA organization must be viewed as essentially experimental, since the concept of incorporating the diverse opinions and experiences of several separate field research centers may in retrospect be judged too ambitious or perhaps even naive. While each STS payload may have unique characteristics, and the project should formulate its own criteria for environmental design, testing and evaluation, a reference source document providing coordinated standards is expected to minimize the duplication of effort and limit random divergence of practices among the various NASA payload programs. These standards would provide useful information to all potential STS users, and offer a degree of standardization to STS users outside the NASA organization.
During the last several years, J.P.L. has evaluated a number of different types of frequency standards. These evaluations include measurement of environmetal susceptibilities (barometric pressure, humidity, temperature and magnetic field) and evaluation of stability. Data from these tests are presented for quartz oscillators, rubidium vapor standards, cesium beam standards, hydrogen masers (active and passive) and a superconducting cavity stabilized oscillator. Data on reliability and mechanical ruggedness based on actual field use is also presented. A survey of new frequency standards, their likely performance and environmental characteristics is presented.
The background leading to the adoption of a Langley Research Center wireframe geometry format standard, a detailed description of the standard, and recommendations for use of the standard is given. The standard chosen is flexible enough to describe almost any complex shape.
NASA has chaired the Consultative Committee for Space Data Systems (CCSDS) for the past four years. During that time, a top-level, end-to-end reference model for space data sytems has been developed that identifies the functions anad services which must be provided by space data systems, and defines the interfaces between major functional elements. A group of definitions for standard protocols has been derived by analyzing these interfaces, and a set of detailed guidelines for space data system standards is in the final stages of negotiation among member CCSDS agencies. Two guidelines that address packet telemetry and channel coding have been approved and are being incorporated into the internal standards of member agencies. Others (packet telecommand, time code, standards data format unit) are in review within CCSDS technical panels and will soon be submitted for approval. These guidelines provide a mechanism for significant cost savings in the implementation of space data systems by allowing reuse of hardware and software for different payloads and for missions, and by enabling the substitution of new technology/higher performance elements at key points in the data system without causing major perturbations in the remainder of the system.